Machine tool control



Feb. 12, 1952 c. JOHNSON MACHINE Toor. CONTROL 2 SHEETS- SHEET l Filed Feb. 14, 1947 Feb. 12, 1952 C JOHNSON 2,585,328

MACHINE TOOL CONTROL A Filed Feb. 14, 1947 2 SHEETS--SIEET 2 1N V EN TOR.

BY l

@www W Patented Feb. l2, V1952 MACHINE rlOOL CONTROL Clarence Johnson, Orfordville, Wis., assignor to Bailey Meter Company, a corporation of Dela- Walle.

Appl'cationFebruary 14, 1947; Serial No'. 728,658

Claims. (Cl. 90-2`4.3)l

My invention relates to machine tool controls in general, and more particularly' to hydraulic pneumatic controls for a machine tool planer.

Planers, as is` well known, operate basically upon the principle of moving a workpiece with a reciprocable motion relative toa tool. The tool remains stationary during the cutting stroke, and is moved laterally or'vertically at the endv ofithe stroke when the workpiece and tool are disengaged. llaners of thisA type, prior to the development of the present invention, were normally con trolled by manual operation of theA tool relative to theA workpiece, or-operated by a seriesof mechanical` movements. For many types of` Work this manual or mechanical controlI of the tool relative to the workpiece. wasr entirely satisfac'n tory, because accuracy within aA few thousandths an inch wasv tolerable: However; for` Work which requires an extremely'closeLtolerance, these controls are entirely unsatisfactory; Nevertheless, nothing better was known and' therefore much handwork was often required to' grind: and nt the workpieces after the machining was iinished; One example of' a typical workpieceV requiring close tolerances, isa spiralling rotor-for a rotary blower; such as usedl with large diesel engines. These rotors for the blower comprise three spiralling lobes on ea-ch rotor, and employ a righi-hand anda left-hand rotor. These righthand and left-hand* rotors must iit' togetherand roll togethertightly in order that air willk not leak past the lobes and reduce the eiiiciency of' the blower. Accordingly, extremely close tolerances must be held to produce aV workable blower-machine. With mechanical methods-of tool control; in producing theserotors on a planer, applicant was faced with the distressing problem oi spend` ing many hours more time in grinding and ittingthe rotors together' after machining than was originally required for the machining operation.

Accordingly7 an object ofV my invention isv to provide a control system to accurately position the tool holder of a machine tool relative' to alongitudinally reciprocating workpiece holder.

Another object oi my invention is to provide of'a control system for the reciprocating cycle of a machine tool planer, including a master control to holdy or hydraulically lock the tool in a iiXed position for cutting the workpiece during the work cutting portion of the cycle, and an indexing control responsive to a pneumatic tracer device scanningl a pattern to index or reposition the tooll relative tothe workpiece during the indexing interval at' the end of' the cutting period.

A- further object of my invention is to provide an oscillatory rotating device for a machine tool planer work holder adapted for eXtreme accuracy of the oscillatory rot-ation throughout all portions ofr the rotating and reciprocating cycle.

Other objects and a fuller understanding of'my invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawing, in which:

Figure 1 is a schematic illustration of my improved machine tool control, including a compensating oscillatory rotation control;

Figure 2is a schematic illustration of an alternative oscillatoryl rotating mechanism; and

Figures 3, 4, 5 and 6 are schematic illustrations of the master control template operation.

The illustrations oi the interconnecting tubes and various members of my apparatus are schematic,v but it is' submitted that these illustrations will readily be understood. Although these various parts and interconnecting tubes could actually be employed as illustrated in the Figure l, it isy of course understood that the practical application would require convenient location of the automatic and manual controls relative to the machine; However, the interconnection between the various members, and their relative location will remain essentially as illustrated in the Figure 1. The necessary parts of the machine tool planer, for'the purposes of this disclosure, are illustrated with the control system, and are essentially the arrangement as found on the open meansof mounting pins l2 upon the reciprocable position locking means for entrappingluid in ai bed. i0. Ihave chosen to illustrate my control system witha helically spirailed workpiece l l because this workpiece was the first for which a full-size machine was fully equipped with my improved control system. It is understood, that this type workpiece is illustrated only for the purpose ofV explaining my improved control system, and is not intended to limit the control system for this particular workpiece.

Generally stated,` my invention comprises` ay master control to hydraulically lock the tool oi the planer in a iixed position for cutting the workpiece during the work cutting portion of the reciprocating cycle; an indexing control responsive to a, pneumatic tracer device scanning a pattern to index or reposition the tool relative to the workpiece during the indexing interval at the end of the cutting period; and an oscillatory rotation mechanism for workpieces of the type to be oscillated about a longitudinal axis as Well as reciprocated during the work cutting period.

In order to oscillatorily rotate the workpiece I I upon the mounting pins I2, I have provided sine bar ways I3, a pinion gear I 8 and a rack I4 extending to the ways I3. The pinion gear is drivingly mounted on pin I2. The rack I4, in the embodiment illustrated in the Figure 1, is dividedv into a toothed portion I and a bracket portion IS. Inter-connecting between the toothed portion I5 and the bracket portion I6 of the rack I4, I have illustrated a small expansible contractible hydraulic chamber l1 and ram adapted to adjust the distances between the portions I5 and I6 of the rack I4, in order to compensate for mechanical misadjustment and wear in the rack and pinion I4 and I5, and the ways I3. The helical spiral is generated by means of the ways and the rack and pinion rotating the pin I2. The rotor lobe shape is generated by a combination of crank and positive motion cam. The sine bar ways I3 Wear rapidly, and it is difficult to set the lead exactly from left to right. Also, there is some lost motion between the sides of the track in the ways I3 and the bracket I6 which reproduces the lost motion as irregularities directly on the work. Without the use of my improved expansible contractible chamber I1, the accuracy of the entire oscillatory rotation of the workpiece I I would be dependent primarily upon the mechanical tolerances between the bracket portion I5 and the Ways I3. Further, slight inaccuracies in the directional placement of the ways I3 would produce an irregular and undesirable oscillatory rotation of the workpiece I I. In order to correct the inaccuracies described, the expansible contractible chamber I1 is provided, and the expansion and contraction of the chamber is accurately controlled by the oscillatory rotation system.

The oscillatory system includes a tracer assembly 23 having a tracer arm 24 adapted to scan a pattern 25. Certain of my prior patents and applications have described a tracer mechanism which may preferably be employed in the present invention. In simplest language, the tracer which scans the pattern provides a valve or port bleeding a pressure iuid such as compressed air to the atmosphere from a substantially constant pressure source. The rate of bleed to atmosphere is determined by the freedom of the port under the dictate of the tracer and pattern. The preferred form of my oscillatory system employs a tracer discharging air under a pressure in the order of 35 p. s. i. freely to the atmosphere at a controllable rate. Air under pressure from any convenient source is conveyed to the tracer assembly 23 through pipe 2I, a pressure regulator I3, and an orifice 2D to a pipe 25 connected with the tracer assembly 23. Air is discharged from the tracer assembly 23 through convenient outlets including the exhaust port 28.

As described in the application above referred to, movement of the tracer arm 24 will permit a variable amount of air to discharge from the tracer assembly 23. In the embodiment of the invention as illustrated in the Figure 1, the rack 14, which extends past the gear I8 is employed as a carriage for the tracer 23. Also, the pattern 25 is provided with an active contact edge 21. This edge 21, and the ways I3 should extend in exactly parallel relationship in a perfect assembly. Therefore, if the ways I3 are placed exactly right, and provided there would be no looseness of iit between the bracket I6 and the ways I3, the tracer assembly 23 should be carried along the edge 21 of the pattern 25 with such accuracy that the tracer arm 24 would remain stationary with respect to the bracer 23, and discharge a steady stream of air to atmosphere. Of course, such an ideal condition is practically unobtainable mechanically. Therefore, the tracer arm 24 will be activated to discharge a variable amount of air to atmosphere. As the air discharges from the tracer 23 to the atmosphere, the pressure in the pipe 26 between the orifice 20 and the tracer assembly 23 will vary, and such controlled air pressure is adapted to affect movement of a bellows 30 of a pilot valve assembly 3l. I illustrate a fluid pump and motor assembly 33 with a supply of fluid in a sump 34. Fluid under pressure is supplied to the pilot valve 3| from the pump 33 through a supply line 35. The pilot valve 3I is sensitive to the slightest pressure changes in the bellows 30 to direct fluid to one end or the other of the chamber I1 through pipes 36 and 31. Drainage from the chamber I1 through the pilot valve 3I is returned to the sump 34 through a return header 38.

When the oscillatory rotation control is used for a blower rotor workpiece II as illustrated in the Figure 1, it is of course desirable that the tracer edge 21 be perfectly straight and accurately aligned. If the Ways I3 are misaligned to some extent, the movement of the workpiece II will still be accurately controlled by my improved control system described, because the template 25 may be moved to position the contact edge 21 in such a position as to give perfect oscillatory rotation control. Further, if any curved or irregular surface should be desired on another type of workpiece, the contact edge 21 may be curved or otherwise formed to control the movement of the workpiece II.

Figure 2 of the drawing illustrates a second embodiment of the portion of my invention adapted to control the oscillatory rotation of the workpiece II. The Figure 2 is a schematic illustration showing the interrelation of the reciprocable bed IIJ and the workpiece II, with the workpiece II mounted on pins I2. The pinion gear I8 is mounted to drive pins I2, and a rack 39 is engaged with the pinion gear in a manner similar to the rack portion i5 illustrated in the Figure 1. An expansible contractible chamber 40 of the servo-motor type is mounted upon a bracket 4I to reciprocate with the bed I5. In this embodiment, the chamber 4i) has a considerably longer stroke than the chamber I1 of Figure l. Thus, instead of merely compensating for inaccuracies, the chamber 43 may be controlled by substantially the same control apparatus described in connection with the chamber I1 of Figure l, and the entire movement provided by the chamber 4U. Thus, as the bed I0 reciprocates and carries the tracer 23 along the tracer edge 21, the chamber 4i! will reciprocate the rack 39 to provide the oscillatory rotating movement to the workpiece II.

'Ihe drawings, as before stated, are schematic. Therefore, it is understood that wherever relative movement is required between units interconnected by tubes or pipes the tubes or pipes are of a flexible design capable of conducting uids under pressure. These flexible tubes are commercially available today.

The indexing control and master control provides for relative movement' of?, the. tool' holder; relative to the workpiece holderfand. is illustrated:l schematically in the Figure 1 ofthe: drawing; A tooliliolder t3 is moved relativeltotheplaner and workpiece; in a lateral direction; by means of a servo-motor 5.1, and vertically`v by means,- of' ai servo-motor Sii. Bower means is.: provided for. reciprocably'driving thebed lila-to moveith'e workepiece l! longitudinally relative tothe; toolL 2.9..' Thus, the'. workpiece. is'v carried in a1 complete; workr cycle including. a Work cutting: portion of.` the cycle for cutting. thewcrkpieicep and an` in.- dexing. intervaLin.. which4 the tool and; workpiece are separated, and duringwhich: time l; have.pr.ovided.' for indexing. or'repositioning the. tool for: the next progressiveV work cutting: period of thev4 work cycle. Basically, the; appavtatusrtor'produc-v ing thev relative4 movement. and work. cycle* control. includes a pattern 45t-, apneumatic. system` includinf-T a tracer producing a: varying, pres surein a header. pipe La hydraulic power systemresponsive to the variations in. pressure-in the header'ii'i adapted to move thetoolholder 48. during the indexing intervaLanda master control system including a master control valve 58A for preventing the ow of iluid to. the-power. sys tem and thereby locking the power system against. movement during the cuttingf period of the Work cycle, and allowing the flow oi fluid. tothel power system to index the tool during the. indexing period of. thework cycle-- The pattern or templateA 45 has a shape cor responding tothe desired path of movement-oi'. the tool to p-roduce the desired iinished workpiece. By corresponding is meant. that the pattern or template should preferablyv corre-- spond to the desirediworkpiece, but isnot necessarily identical in contour, andv therefore the term corresponds implies that the pattern or: template is purposely designed toresult in. the desired contour of. the; workpiece to. heproduced.

In the Figure l, air under pressure from. any. convenient source is conducted tothe header 4'!- through pipe 2l. Although the pipe. 2l is the. same lead pipe feeding the pipe 26. and. tracer, 23, any suitable air. source maybe enfiployed,` and. it is not intended that the various systems are dependent uponione another-by: theshowng of only one air supply. The air from thev pipe 2! is passed through. a pressureregulator 49 and an oricel- 5.0 tothe header 41 and tracer 45. .Air4 may he discharged from the tracer 45y through port 32. As the air discharges` from. the tracerll to the atmosphere the pressure inthe hea-der il between. the orifice 5D andthe tracerassembly will vary. such.v controlled air pressure. .is representative of changes in contour of! the pattern 45.

Movement of the tool. holder 4.1i in. a. laterali direction is produced. by aservo-motor 5L This type of motor, as is well known.. comprises a. chamber with. a piston therein and ai rodextending out one endr of the cylinder. Fluid" under pressure from the pump 33 is conductedlto. a manually operable dn'ectionvalve 52 through.. a pipe. During the indexing interval of the, workoperation, the tool holder progresses from. right to left, transversely,. in.. the Figurev 1., and. therefore the direction valve is positionedto ccnduct the. hydraulic pressureffrom. the pipe 53 to. a lead pipe Se going into the leftehand end' of. the motor 5l. With fluid feedingiintothe leithandend of the motor chamber, pressure-willbe: exertedl through. the rod 55 againsty the, sidefof. the. machine; and., the. tool. holder will be movedv 70? tu, ai. manually`V operable`v lay-pass. valve. 'i 3;

toward thealeft.. Eliidiisintroducedinto;theronex side; of'the: piston and; exhausted; from; the other' side; toicause; movementf of'v the rod irr one direc;- tion, and: therow: reversed to cause movement-` of: the rod in: theoppositadirection; Therefore, withv thefuidentering the motorY 5ll through the pipe 54;. exhaustifluid will be. conductedY out of thevmotorxSl through'thepipeir This exhaust. through the pipe: Eis conductedtothe-valve 52 andl out through. the.A pipe- 5l InrnyI in'lprovedsystem,v the fluid is conducted to. the;pipe 5,1- into a master control valve 58. The. fluid. then; leaves they valve 58v through a: pipev 5.9 and, is conducted byI the; pipe 591 to amanuallyK operated feed control valve 6B; During: the indexing interval of the Work operatiom, the speed of the.motor;5il should` be relatively low, and llhavexprovided a. speed .control or resistance.- valvefil ofi improved. designcapable of adjust menti; by means ofv a. hand adjustment S2 for preselecting the.n maximumV operating speed of; theamoton'i. Further, the valve @l is responsivezto the; variable.` pressure in the header 6l'. to; further control the speed" of. the. motorl 5| in accordance, with.v the; template.l 45. During the'- indexing intervallofthe Work'. operation, fluid is= conducted' through; the pipe 63' from the valve Mitos-the valve'-6l.. Fromfthevalve 6l, the fluid isf theniexhausted; to, the sump through'` a pipe 64. However, if rapid operation of the motor. Ezl is; desiredi during themachine set up, or to movey the tool. out, of. contact with the work for some reasonthe.I feed control valve Ell may` hev moved; to conduct the iiuid. from the pipe e9 directlyftthe; pipe;4 65 for: direct return to thesunrpi and;bypass;of the-valve 6 I, wherebyl rapid movement will he obtained.`

Aisecondiservo-motor 66r is employed to move` the: toch holden: 48;l ina. vertical direction rela-- tivevtd the: workpiece: H. The motor is of substantially the?, same.: type;A asr thev motor 5I. Fliidxunderpressure;iszfed to the control system for tire -motoriiG-i through; a, supply pipe 22f leading from, the: pipef351 andthe pump 33. This uidisadirected: by.l a1 pilottvalve S1 toeither the topior'bottcrn of; the motor 6.6; or may operate tot; on, ther now of oil altogether andv trap the; oilon; both sides: of the; motor piston in ordertozlioldf; the motor: andtool. holder 43 statierra-ryu.v Although; the. motor 56 moves both upwardly-fand downwardly under the dictateof the pattern: 6155,'. rathervr than. predominantly in ones. direction of: travel; asf. indicatedI in connectionzwitln the: motori-5 I3.. it will be apparenti fromthe location: on the` tracer' 46 relative;v to.- the; template-d5.; that; the-direction of travel in the illustrationwill beupwardly. Accordingly, uid is:fed:through the; pilot valve l to the lead pipe' 68; going into. the bottom portion of the motor 66. Fluidis accordinglyI exhaustedfrcm the top:

part of: the, motor 6,6' through pipe` 69. This exhaust'. Huid istconducted. through the pipe 63- toa maximum: speed valve 10. As indicated in the illustration. the; maximum speed valve 7B" may be hand;l adjusted; by means.l of' acontrol 'Hi t'of pred'etermine;` themaximum rate of ilow of iluid therethrough and consequentlythe rate of'; movement;` of' the motork 65. Fluid is then conducted, from the. valve 1n through pipe l2.: Also,. a; 'I4 is: provided to, lay-pass the valve 1!! directly` to,` thefbyi--passV valve.. '13.y Therefore, the operator; may pre-select the position of the valve- 131 to direct the. exhaust :fluidv from the. motor 66 throughthe maximum speed valvel, or may 7 direct the uid through the by-pass line 14 for rapid operation. In either case, the fluid is conducted from the valve 13 through the pipe 15 and the pilot valve 61 to the sump 34.

As thus far described, therefore, my improved apparatus includes a pilot valve 61 controlling the direction of vertical movement of the tool holder 48 in response to a pattern 45 and tracer 46; a resistance Valve 6I automatically slowing the speed of horizontal movement in accordance to the dictates of the pattern and tracer control, and at the same time being manually adjustable in the amount of automatic control; and four manual controls 52, 6U, 1U and 13, for manually controlling the direction and speed of operation.

The third portion of my improved control system comprises a master control system for hydraulically locking the motors and 6B against movement during the cutting period, and releasing the motors to the control of the pattern and tracer during the indexing interval. This control4 system includes a convenient source of air pressure, again the source conducted through the pipe 2|, a pressure regulator 18, and an orice 19. A tracer 80, similar in construction to the tracers 23 and 46, and`exhausting air to atmosphere through port 42, is conveniently mounted on a stationary portion of the machine tool.

An actuating member 8|, as illustrated in Figures 3, 4, 5 and 6 of the drawings, is reciprocably carried by the reciprocating bed l0. A1- though the tracer 8U and the actuating member 8| are illustrated beside the reciprocating bed I9, any convenient location may be employed.

The member 8|, I have found, is preferably formed to actuate the tracer 80 for an interval of time in order that the master control valve 58 will be moved to a release position, whereby iluid may momentarily flow through the valve 58 to the motor 5| to permit the motors 5| and 66 to operate as previously described. The interval of time, on a planer, I have found, need be in the order of a small fraction of a second.

In the Figure 3, the actuating member 8| is pivotally mounted by means of pin 85. A spring 8B is provided to urge the member 8| to a rest position against a stop member 81, as illustrated.

As the member 8| moves with the bed I8, a cam edge 88 of the member 8| contacts the feeler arm 89 of the tracer 80 and actuates the arm 89 momentarily out of its rest position, and disturbs the air flow from the tracer 80. It is during this short period of disturbance that the indexing of the tool holder 48 takes place.

The member 8| is so located with reference to the tracer 80, that the member 8| will actuate,

the feeler arm 89 as soon as the tool 29 is separated from the workpiece at the beginning of the indexing cycle. Thereafter, the member 8| will pass beyond the arm 89 as the bed I8 moves to the end of its reciprocating cycle. See Figure 5. During this interval, the entire indexing and master control system has time to "settle down before the tool 29 again engages the workpiece In the Figure 6, which illustrates the return stroke of the bed |9 and member 8|, the member 8| is shown pivoted by contact with the feeler 89. The feeler 89 is movable in only one direction, and therefore the air pressure in the pipe 82 is not disturbed by such contact in pivoting the member 8|. After the member y8| has moved beyond contact with the feeler arm 89, the

spring 86 is adapted to pivot the member 8| back into the position illustrated in Figure 3 against the pin 85.

Thus, the tracer 88 discharges a fixed amount of air to atmosphere at all times except for the brief moment when it is actuated by the member 8|. A pipe 82 conducts air from the orifice 19 to the tracer 89 and serves as a header pipe. Therefore, there is a given amount of pressure in the pipe 82 until the tracer 80 is actuated by the member 8|, and then the air pressure will be momentarily disturbed in the pipe 82. A bellows 83 is adapted to respond to that disturbance in pressure and move the master control valve 58. As illustrated in the Figure 1, the member 8| is out of contact with the tracer 29, and therefore the normal undisturbed pressure is prevailing in the pipe 82. Under this set of circumstances, it is desired that the tool holder 48 be locked in its position, because it is in contact with the workpiece Therefore, the inner portion of the valve 58 is in a fluid blocking position as illustrated in order to block off the passage of fluid from the motor 5| through the pipes 56, 51, 59, 63 and 64. Therefore, the motor 5| is stopped, and lateral movement of the tool holder 48 and the tracer 4E is arrested. Because the tracer movement has been arrested, discharge of air to atmosphere through the header 41 will be at a constant rate, and the pilot valve |51 will be positioned as illustrated to block off the passage of iluid to or from either side of the motor 55, and consequently the motor 86 will also be locked in its position.

In operation, when the pump 33 delivers fluid under pressure, the tendency will be for the motor 5| to move the tool holder 48 at a predetermined rate to the left in the illustration. As this movement normally progresses, the tracer 48 is carried therealong and scans the template 45. Hydraulic motor controls operate in response to the tracer relationship to the template in order to position the tool holder 48 relative to the workpiece However, in planer operation wherein the workpiece reciprocates relative to the tool in the tool holder 48,

. the tool may be indexed only during the indexing period of the work cycle. In machine tool practice, the reciprocation of the bed I8 is so fast that the tool is out of contact with the workpiece for only a brief interval in the order of a fraction of a second during the indexing interval. It is during this interval that the member 8| actuates the tracer 80 and upsets the air balance in the pipe 82. However, the bellows 83 is able to move the valve 58 and allow fluid to pass therethrough for a long enough period of time for the motor 5| to move the tool holder laterally, and for the tracer 46 to respond to the shape of the pattern 45 and cause vertical movement of the motor 66. Therefore, my invention supplies an improved indexing mechanism for the movement of the tool, and provides master control to lock the tool against indexing movement during the cutting period of a work cycle by permitting the indexing mechanism to completely control the tool during the indexing interval. My invention also supplies an accurate oscillatory rotation movement of the reciprocating workpiece during the work cycle. l

When machining the particular workpiece illustrated, the entire profile may be made completely around the workpiece by forming the pattern 45 to correspond to 120 of the 360 cir- -cumference Vin the workpiece.

The workpiece isthen repositioned three times for one complete machining operation. Therefore, by forming the pattern e to correspond'to 120 of thecircumference, the workpiece Il lmay be repositioned after the tracer `46 has traversed the pattern 5.5, t is apparent therefore, that `my control system `embraces a new type tracer pattern method wherein the machine tool is indexed relative to the workpiece through asequence of movements which will be repeated a plurality of times in order to produce ya complete prole on the finished workpiece. By this provision, the complexity of the indexing mechanism is greatly reduced, and the efficiency of vthe Vmachine tool increased.

Although I have described my invention with a certain degree of particularity in its preferred form, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement oi parts may be resorted to without departing from thespirit and the scope of the invention as hereinafter claimed.

What is claimed is:

1. In a machine tool having a tool holder and a reciprocating workpiece `holder moving in a work-cycle including a cutting period and .indexing interval, the provision of apparatus for relatively moving the tool holder and workpiece holder', comprising indexing means including a pattern, a lirst substantially constant air supply, tracer means exhausting air to atmosphere `from said iirst air supply ata variable rate in `response to the form of said pattern, said variable rate of exhaust producing a variable pressure between said air supply and said exhaust means, first pressure responsive means responsive to said variable pressure, a first hydraulic system including a piston for moving the tool holder in a iirst direction, a second hydraulic system including a piston for moving the tool holder in a second direction, said first and second hydraulic systems being controlled by said rst pressure responsive means, and master control means, said master control means including hydraulic entrapment valve means having a rst position for entrapping fluid in said first and second power systems to lock said power systems against movement, and having a second position releasing said iirst and second power systems to the control of said rst pressure responsive means, a second substantially constant air supply for said master control, trip means exhausting air to atmosphere from said second air supply at a rst rate during the cutting period of the work cycle, trip actuating means responsive to the reciprocating movement oi the work holder adapted to actuate said trip means during the indexing interval of the work cycle and cause said trip to exhaust air at a second rate from said second air supply, second pressure responsive means between said second air supply source and the trip means, said second pressure responsive means being responsive to the first rate of discharge to operate said hydraulic entrapment valve to said rst position and lock said rst and second power systems against movement, and responsive to said second rate of discharge to operate said hydraulic entrapment valve to release the first and second power systems to the control of the pneumatic tracer system.

2. In a machine tool having a tool holder and eciprocating motion in a direction airsupplyat a variable rate in response to the l form of said pattern, said variable Arate of exn .haustproducing a vvariable pressure between said `air `supply `and said exhaust means, rst means .responsive .to lsaid variable pressure, a rstfpower systemior moving the tool holder in a rst direction, alsecond power system for moving the .toolholder inra second direction,fsaid rst and vsecond power systems being controlled by said .first pressure responsive means, said rst and second directions being in one plane, said workpiece holder being adapted vto move with ka reluostantially at -rightanglesto said plane, and master control means, said `master control'means including po sition locking means `for ysaid first and second power systems, a second substantially constant air supply lfor said master control, trip means exhausting air to atmosphere from said second air 4supply -ata first rate during the work period of the work cycle, trip actuatingmeans responsive to the reciprocating movement of the work holder adapted to `actuate said trip .means during the indexing intervalland cause said trip to exhaust air at a ysecond rate from said second air supply,

second .fpressure responsive means between said seconde-air supply-source andthe trip ln'leansvsaid second pressure responsive means being responsive to the rst rate of discharge from said trip means tooperate said position locking means to a locking position and lock said rst and second power systems against movement, and responsive to said second rate of discharge to operate said position locking means to a release position and. release the rst and second power systems to the control of the pneumatic tracer system.

3. In a machine tool planer having a rotatable reciprocating work holder movable in a work cycle including a work cutting period and an indexing interval, and a tool holder movable through an angular path relative to said work holder, an indexing means including nrst pattern controlled pneumatic indexing means, and rst hydraulic motive means for positioning the tool holder along said angular path relative to the workpiece holder, a master control means including hydraulic entrapment means having a locking position adapted to entrap hydraulic iiuid in said first hydraulic motive means and lock the rst hydraulic motive means against movement, and having a release position adapted to place the rst hydraulic motive means under the control of said rst pattern controlled pneumatic pressure means, trip means, interconnecting means between said trip means and said hydraulic entrapment means, means responsive Ito a relative position of the Work holder and tool holder during the cutting period to actuate said trip means to a rst position and actuate said interconnecting means to move said entrapment means to said locking position, and responsive to the indexing interval position of the work holder and tool holder to actuate said interconnecting means to move said entrapment means to said release position, and work holder rotating means, said rotating means including rack and pinion means, way

means, bracket means adapted to slidably engage said way means, hydraulic expansible contractible means interconnecting said bracket and rack, and second pattern controlled Pneumatic pressure means, said expansible contractible means being under the control of said second pattern controlled pneumatic pressure means to adjust the position of the rack relative to said Way means.

4. An oscillatory rotating control for a machine tool Work holder, comprising rotatable mounting means for a workpiece, rack and pinion means to oscillatorily rotatably drive said Work holder, expansible contractible hydraulic means drivingly attached to said rack, footing bracket means to position said expansible contractible means relative to said pinion, a pneumatic tracer system for controlling said expansible contractible means, including a substantially constant air supply, tracer means, pattern means, means to move the tracer responsively to the rack movement and relative to the pattern, said tracer exhausting air to atmosphere from said air supply at a variable rate in response to the form of said pattern, said variable rate of exhaust producing a variable pressure between said air supply and said tracer, pressure responsive means responsive to said variable pressure, pilot valve means directing uid to said expansible contractible means, said pilot valve being controlled by said pressure responsive means.

5. An oscillatory rotating control for a machine tool Work holder, comprising a longitudinally reciprocable and rotatable mounting means for a workpiece, rack and pinion means reciprocably carried with said mounting means to oscillatorily 12 rotatably drive said Work holder, Way means extending at an angle to the path of said longitudinal movement of the work mounting means, bracket means slidably attached to said way means, expansible contractible hydraulic means interconnecting said rack and bracket, a pneumatic tracer system for controlling said expansible contractible means including a substantially constant air supply, tracer means, pattern means, means to move the tracer responsive to the rack movement and relative to the pattern, said tracer exhausting air to atmosphere from said air supply at a variable rate in response to the relative position of the tracer and pattern, said variable rate of exhaust producing a variable pressure between said air supply and said tracer, pressure responsive means responsive to said variable pressure, pilot valve means directing fluid to said expansible contractible means, said pilot valve means being controlled by said pressure responsive means.

CLARENCE JOHNSON.

REFERENCES CITED The following references are of record in the ile of this patent:

UNITED STATES PATENTS Number Name Date 2,101,712 Johansen Dec. 7, 1937 2,154,718 Bannon Apr. 18, 1939 2,402,450 Salisbury June 18, 1946 2,420,547 Lovely May 13, 1947 2,436,373 Barnes Feb. 24, 1948 2,485,716 Eberlein Oct. 25, 1949 

